Marine-grade aluminum is used for commercial ship building and in the manufacturing of boats and marine vehicles. According to Total Materia, the 5xxx series grade of aluminum features magnesium as its major alloy, which adds to the durability and corrosion-resistance feature of the marine-grade product. However, the metal may be vulnerable to cracking due to stress or intergranular corrosion.
According to Total Materia, aluminum grades, such as the 5xxx series, display a broad range of properties depending on the heat treatment or alloying elements that are used. Considerations for use include an alloy's appearance, level of corrosion resistance, strength-to-weight ratio, weldability, fracture toughness and ease of fabrication.
High temperatures can cause marine-grade metal to become susceptible to stress corrosion, leading to cracking in the hulls of ships. According to the Alcoa Company, their H128 grade of marine aluminum is made to provide extra corrosion resistance in this respect.
The Nautic-Al alloys possess excellent thermal stability, thereby reducing the risk of corrosion and costly repairs. The H128 alloy meets U.S. Navy corrosion tests for planned service life and is registered with the U.S. Aluminum Association. According to Alcoa, the tempered alloy has received a marine certificate for civil shipbuilding by the Lloyd's Register as well.
The Bodycote website defines tempering as a heat treatment process that is generally performed after hardening during metal manufacturing. The goal of tempering is to ensure that a metal meets the specifications set for use in a specific series of aluminum elements.